Vortex tube

ABSTRACT

The invention relates to a vortex tube ( 1 ) for the generation of cold air. The vortex tube comprises a tube body ( 2 ) with a wall ( 5 ), the inner wall surface ( 6 ) of which forms a channel ( 7 ) with a circular-cylindrical cross section. A vortex generator ( 8 ) is arranged in a first end ( 9 ) of the channel ( 7 ) and a flow limiting body ( 10 ) is arranged in a second end ( 11 ) of the channel ( 7 ). One or several outlet/s ( 12 ) for hot air is/are arranged at the second end ( 11 ) of the channel ( 7 ). The vortex generator ( 8 ) has an opening ( 13 ) through which cold air may leave the channel. A conduit ( 14 ) for the supply of compressed air to the vortex generator ( 8 ) runs through the wall ( 5 ) of the tube body ( 2 ) in parallel with the inner channel ( 7 ) from a rear end ( 3 ) of the tube body ( 2 ) up to an inlet ( 15 ) to the vortex generator ( 8 ).

This application claims priority to Swedish Patent Application No. 0800805-4, filed on 10 Apr. 2008, the complete disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a vortex tube designed to generate cold air.

BACKGROUND OF THE INVENTION

A vortex tube, also known as Ranque-Hilsch tube, is a device which is used in such cases where one wants to generate a flow of cold air. A field of application for vortex tubes may be cooling of tools, for example grinding discs. Other fields of application comprise cooling of coatings within the plastic industry, for example. In a vortex tube a flow of air is sent through a vortex generator that causes the air to rotate and a vortex of air to move inside a tube. In a second end of the tube the air vortex meets a resistance and the air flow is divided into two parts, one flow of cold air and one flow of hot air. The cold air flow moves backwards in a direction towards the vortex generator and out through a central opening therein. The hot air flow leaves the vortex tube through another path. Vortex tubes according to prior art are described in EP 1 396 690 A1 and U.S. Pat. No. 3,183,273, for instance. A conceivable theoretic explanation of the effect of the vortex tube may be that the part of the air flow, which turns back at the resistance, delivers thermal energy to the air vortex moving forwards in a direction towards the resistance.

An object of the present invention is to provide an improved vortex tube. In this context, it is, inter alia, an object to give the vortex tube a more compact design.

DISCLOSURE OF THE INVENTION

The present invention relates to a vortex tube for the generation of cold air. The vortex tube comprises a tube body with a wall, the inner wall surface of which forms an inner channel with a circular-cylindrical cross section. A vortex generator is located in a first end of the channel and a flow limiting body (a resistance) is located in a second end of the channel, and an outlet for hot air is also arranged at the second end of the channel. The vortex generator has an opening, through which cold air may leave the channel in the first end of the channel, and further the vortex tube has at least one conduit for the supply of compressed air to the vortex generator. Said at least one conduit for the supply of compressed air extends in the same axial direction as the tube body and runs from a rear end of the vortex tube up to an inlet to the vortex generator, and the rear end of the vortex tube is adapted to be connected to a source of compressed air.

In an embodiment, said at least one conduit for the supply of compressed air extends/runs from a rear end of the very tube body through the wall of the tube body in parallel with the inner channel. However, embodiments are conceivable, where this is not the case.

In some embodiments the vortex tube has a plurality of conduits for compressed air extending/running through the wall of the tube body in parallel with the inner channel. The conduits for compressed air may then be distributed around the circumference of the tube body, and preferably they are evenly distributed around the circumference of the tube body to give a uniform flow in the inner channel of the vortex tube.

The outlet for hot air, which is arranged in connection to the second end of the channel, is preferably designed to discharge hot air radially outwardly from the tube body.

An axially adjustable first sleeve may possibly be arranged on the tube body in connection to the outlet for hot air, so that, by means of axial displacement of the first sleeve, one can adjust the size of the outlet for hot air.

The vortex generator may be designed so that it has passages, which at first converge and then diverge in a direction from the inlet of the vortex generator and towards the inner channel of the tube body.

The vortex tube may comprise a valve, which is arranged to be axially displaceable into the vortex generator or out of it, so that a flow of air through the vortex generator may be adjusted thereby. According to one embodiment, such a valve may be arranged inside a second sleeve. Said second sleeve has a first end which is threaded onto the tube body so that, by screwing/turning the second sleeve, one may adjust the position of the valve in relation to the vortex generator. Said second sleeve has an outwardly open second end through which cold air may flow out.

The second sleeve may possibly comprise one or more vanes arranged between the valve and the outwardly open second end of the second sleeve. Such vanes are arranged at least partly to convert a rotating air flow into a straight air flow.

The second, outwardly open end of the second sleeve may possibly be toothed along its circumference so that an air flow from the vortex tube is not blocked if the outwardly open end of the second sleeve would be pressed against a hindrance.

A sound-absorbing filter may be arranged on the tube body around the region of the outlet/outlets for hot air. The sound-absorbing filter is suitably designed as a sleeve.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a schematic cross section of a vortex tube according prior art.

FIG. 2 is a side view of a first embodiment of a vortex tube according to the present invention.

FIG. 3 shows a cross section of the vortex tube according to FIG. 2.

FIG. 4 a is an enlargement of the region IV of FIG. 3.

FIG. 4 b is a view corresponding to FIG. 4 a but shows how a slightly different embodiment in a disassembled state.

FIG. 4 c is a view corresponding to FIG. 4 a showing the embodiment of FIG. 4 b in its assembled state

FIG. 5 is an enlargement of the region V of FIG. 3.

FIG. 6 is an exploded view in cross section, where the cutting section is made in another plane than in FIG. 3.

FIG. 7 is en exploded view corresponding to FIG. 2.

FIG. 8 is a side view showing one of the details of FIG. 7.

FIG. 9 shows a front end view of the same detail as FIG. 8.

FIG. 10 is a side view of one of the details of FIG. 7.

FIG. 11 is a rear end view of the same detail as in FIG. 10.

FIG. 12 is a front end view of the same detail as in FIG. 10.

FIG. 13 is an enlargement of the region XIII of FIG. 12.

FIGS. 14 to 17 are different views of an additional detail of FIG. 7.

FIG. 18 is a perspective view, partly in cross section, showing two cooperating elements in the vortex tube of the invention.

FIG. 19 is a perspective view showing the same cooperating parts as in FIG. 18.

FIG. 20 is a side view, partly in cross section, of the same details as in FIG. 18 and FIG. 19.

FIG. 21 shows, in a perspective view, another detail of FIG. 7.

FIGS. 22 to 23 show, from the side and in cross section, an additional detail of FIG. 1.

FIG. 24 shows how several vortex tubes according to the invention are attached on a common holder.

FIG. 25 shows how a vortex tube of the invention is placed on an air blow gun.

FIG. 26 schematically shows a second embodiment of the vortex tube of the invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a vortex tube T according to prior art is shown. In FIG. 1 it is schematically shown how air from a source, not shown, of compressed air, is fed into the tube T via an inlet 1. The inlet I is arranged perpendicularly in relation to the longitudinal axis of the tube T. From the inlet I air passes to a vortex generator V, which may comprise vanes or channels (not shown) to put the air into rotation. A vortex of air moves from the vortex generator V and in a direction to the right in the figure. In the right end of the tube T the air vortex meets a resistance M. At the resistance M the air vortex will be divided into a hot air flow leaving the vortex tube through an outlet H and into a cold air flow turning back and leaving the vortex tube through an outlet K for cold air. Vortex tubes of this kind are today used in industrial applications such as e.g. for cooling of tools.

In FIGS. 2 to 25 a first embodiment of a vortex tube I for the generation of cold air according to the present invention is shown, while a second embodiment is shown in FIG. 26.

As may be seen from FIG. 2, the vortex tube I according to the first embodiment comprises i.a. a tube body 2 and a sleeve 21 which may be used for adjusting the air flow in a manner which will be explained later. When the vortex tube 1 is used, cold air exits through an outwardly open end 23 of the sleeve 21.

FIG. 3 shows a cross section of the vortex tube shown in FIG. 2. As may be seen from FIG. 3, the tube body 2 has a wall 5, the inner wall surface of which forms a channel 7. The channel 7 has a round circular-cylindrical cross section.

FIG. 6 shows an additional cross section of the vortex tube 1 according to the first embodiment. Here, the crosscut has, however, been made in another plane and the vortex tube is shown dismounted into its components. As may be seen from FIG. 6, the channel 7 has a first end 9 and a second end 11. A vortex generator 8 is placed in the first end 9 of the channel 7, and a flow limiting body 10 is placed in the second end 11 of the channel. The flow limiting body 10 is a resistance which serves basically the same function as the resistance M in the vortex tube according to FIG. 1. At least one outlet 12 for hot air is arranged at the second end 11 of the channel 7. In certain embodiments of the invention, several outlets 12 for hot air may be provided. These outlets 12 are suitably arranged around the circumference of the tube body 2. As also may be seen from FIG. 6, the vortex tube 1 has at least one conduit 14 for the supply of compressed air to the vortex generator 8. Said at least one conduit 14 for the supply of compressed air extends/runs through the wall 5 of the tube body 2 in parallel with the inner channel 7 from a rear end 3 of the tube body 2 up to an inlet 15 to the vortex generator 8. The rear end 3 of the tube body 2 is adapted to be connected to a source 16 of compressed air. In this way, compressed air may be fed into the conduit or conduits 14. In an embodiment of the invention, there is a plurality of conduits 14 for compressed air extending through the wall 5 of the tube body 5, distributed around the circumference of the tube body 2. With such an embodiment a larger flow may be obtained. Further, an essentially uniform flow in the vortex tube may be obtained, which results in a more efficient division of the air flow into a hot and a cold air flow.

In the embodiment shown in FIG. 6, the rear end 3 of the tube body 2 may be seen as a rear end of the very vortex tube 1. Embodiments are, however, conceivable, where the vortex tube I comprises parts lying behind the rear end 3 of the tube body. Such an embodiment is shown in FIG. 26.

A possible embodiment of the vortex generator 8 and its inlet 15 will now be explained with reference to FIG. 10, FIG. 12, and FIG. 18. As may be seen from FIG. 10, the tube body 2 has a rear end 3 and a front end 4. FIG. 12 shows the front end 4 of the tube body 2 in the direction of the arrow B in FIG. 10. The vortex generator 8 may be provided with one or more passages 19 that are directed inwardly towards the inner channel 7 of the tube body 2. In one embodiment, the passages 19 may be designed as laval nozzles, which at first converge and then diverge in a direction from the inlet of the vortex generator towards the inner channel 7 of the tube body 2. Such a design contributes to increasing the speed of the air flow. In this way, a more efficient cooling of air is achieved. This design of the passages 19 is best shown in FIG. 13. FIG. 18 also shows how each conduit 14 for compressed air extends to an inlet 15 to the vortex generator 8. As is best seen from FIG. 12, the vortex generator has an opening 13, through which cold air may leave the inner channel 7 in the first end 9 of the channel 7.

The vortex generator 8 may be made integral with the tube body 2 or it may be manufactured as a separate body which is then mounted onto the vortex tube 1, e.g. by fixing it in the tube body 2.

The idea to use converging/diverging passages may be used also in such vortex tubes where air is transversally supplied like in the vortex tube shown in FIG. 1.

In one embodiment, the outlet 12 (or the outlets 12) for hot air is/are designed to discharge hot air radially outwardly from the tube body 2. Suitably, there is a plurality of outlets 12 distributed around the circumference of the tube body 2. Such a design of the tube body 2 is shown in FIG. 10 as well as in FIG. 11. FIG. 11 shows the rear end 3 of the tube body 2, i.e. in the direction of the arrow A in FIG. 10. As may be seen from FIG. 11, there is a plurality of conduits 14 for compressed air that are distributed around the circumference of the tube body 2. The conduits 14 run parallel with the channel 7.

A possible design of the flow limiting body 10 (or the resistance 10) is shown in FIG. 8 and FIG. 9. In its end facing towards the vortex generator 8, the flow limiting body 10 has been divided into a plurality of vanes 34. These vanes may contribute to control the outer flow of hot air in a direction towards the outlet or outlets 12, when a vortex of rotating air reaches the flow limiting body 10. Embodiments are also conceivable, where the flow limiting body 10 is not provided with such vanes 34.

FIG. 6 och FIG. 7 show that a vortex tube I may comprise a first axially adjustable sleeve 17. The function of this sleeve is more distinct shown in FIG. 5. As is shown in FIG. 5, the sleeve 17 is arranged on the tube body 2 and associated with the outlet 12 for hot air. Through an axial displacement of the first sleeve 17, one may adjust the size of the outlet 12 for hot air. A way of achieving an axial displacement of the first sleeve 17 is shown in FIG. 5. As may be seen from FIG. 5, an outer control sleeve 28 may be placed on the tube body 2 over the first sleeve 17. The outer control sleeve has an inner thread 29 cooperating with an outer thread 30 on the first sleeve 17. The outer control sleeve 28 is stationary in its axial position. When the outer control sleeve 28 is turned, the inner thread 29 of the control sleeve 28 will cooperate with the outer thread 30 of the axially displaceable first sleeve 17 such that the first sleeve 17 is displaced in an axial direction. In this way, one may increase or reduce the available outlet area of the outlet or outlets 12 for hot air.

It should be understood that the adjustment of the available outlet area of the outlet/outlets 12 for hot air which is shown in FIG. 5 may be used also in vortex tubes where the compressed air is supplied from the side in the way shown in FIG. 1.

As an alternative to a separate control sleeve 28, embodiments are conceivable where the axially displaceable first sleeve 17 has an inner thread (not shown) cooperating with an outer thread (not shown) of the tube body 2.

In the example shown, the sleeve 17 is displaced by it having an outer thread 30 which cooperates with the inner thread 29 of the control sleeve. However, embodiments are conceivable, where the sleeve 17 does not utilize threads for displacement of the sleeve. For example, the sleeve could be loosely mounted on the tube body 2 but be so snugly fitted on the tube body that, in order to displace the sleeve 17, the friction must be overcome and a certain force must be used.

As an alternative to the axially displaceable sleeve 17, one may use, for example, a sleeve which, at different angle positions, blocks the outlet/outlets 12 more or less. Such a sleeve may be provided with an opening/openings which correspond(s) to the outlet/outlets 12 for hot air and which may be turned so that they completely or partly coincide with the outlet/outlets 12. The sleeve may then be given such a design that, in one angular position, it completely blocks the outlet/outlets 12 for hot air.

The axially displaceable and/or turnable sleeve 17 thus permits an adjustment of the amount of hot air leaving the vortex tube. This adjustment takes place independently of the total amount of air. Thus, the vortex tube is designed such that the size of the outlet/outlets 12 for hot air can be adjusted. In this way, one can adjust the ratio between the amount of hot air discharged and the amount of cold air discharged. This adjustment is independent of the total flow.

In one embodiment, the vortex tube I further comprises a valve 20, which is axially displaceable into the vortex generator 8 or out of it, so that a flow of air through the vortex generator 8 may be adjusted thereby. An example of a possible design of such a valve is shown in FIGS. 14 to 17. The valve 20 may be designed as a round body, on which a protruding male part 36 has been arranged. The protruding male part 36 is designed to fit into the inlet 15 to the vortex generator and in the passages 19 of the vortex generator. There is an opening 35 in the valve 20, which opening may be centrally arranged in the valve 20. Cold air may pass through the opening 35 in the valve 20 from the tube body 2 and out of the vortex tube. 1.

The dimensions of the male part 36 may be chosen somewhat smaller than the dimensions of the passages 19 in the vortex generator; they may be about 5% smaller, for instance, so a certain play is obtained.

The valve 20 may possibly be manufactured in two parts; one front part 20 a and a rear part 20 b (see FIG. 18, FIG. 20). The front part 20 a may then be an utmost end or the tip of the protruding male part 36 of the valve, while the rear part 20 b forms the main part of the body of the valve 20 and also the base of the protruding male part 36. The front part 20 a may then be somewhat smaller than the dimensions of the passages 19 in the vortex generator; they may be about 5% smaller, for instance, so that a certain play is obtained. The dimensions of the portion of the protruding part 36 belonging to the rear part 20 b may indeed be somewhat larger than the passages 19, say up to 4% larger. In this way a sealing effect is obtained. The valve 20 or at least its rear part 20 b may then be manufactured of a comparatively soft material permitting a certain deformation. For example, the front part 20 a may be manufactured of a material marketed by Bayer AG, Germany, under the trade name Makrolon® 8035. The rear part 20 b may be manufactured of a material commercially available under the trade name Elastollan® C60A HPM which is marketed by Elastogran GmbH (Elastogranstrasse 60, 49448 Lemförde, Germany), a subsidiary of BASF.

The function of the valve 20 will now be explained with reference to FIGS. 18 to 20 and FIG. 4 a. In FIG. 18 a position is shown (exaggerated) where the valve 20 is completely separated from contact with the vortex generator 8. However, the protruding male part 36 is in a position to move into the inlet 15 and the passages 19. FIG. 19 shows, in perspective, how the valve 20 has moved up to the tube body 2 and how the protruding male part 36 has began to penetrate into the passages 19 in the vortex generator 8. In FIG. 20, it is shown how the protruding male part 36 of the valve 20 has penetrated a distance into the vortex generator 8. The same position is shown in perspective in FIG. 19. In this position a portion of the inlet to the vortex generator 8 is blocked and a flow of compressed air through the conduits 14 will be partly throttled. It should be understood that the valve 20 need not necessarily be designed such that both the inlet 15 to the vortex generator and the passages 19 are blocked. For example, the protruding male part 36 of the valve could be designed to enter only into the inlet 15 or to enter only into the passages 19 of the vortex generator. The position of the valve 20 in relation to the vortex generator 8 may be adjusted in different ways. A possible solution will now be explained more in detail with reference to FIG. 4 a and FIG. 4 c. As may be seen from FIG. 4 a and FIG. 4 c, the valve 20 may be arranged inside a second sleeve 21. The second sleeve 21 has a first end 22, which is screwed onto the tube body 2. At its front end 4, the tube body 2 may have an outer thread 41 that can cooperate with an inner thread 40 of the second sleeve 2. By screwing/turning the second sleeve 21 one may force it to move axially on the tube body 2. The valve 20 accompanies the second sleeve 21 in its axial motion. By screwing the second sleeve 21 one may therefore adjust the position of the valve 20 in relation to the vortex generator 8. Thereby, the air flow from the conduits 14 and into the inner channel 7 of the tube body 2 may be adjusted. As may be seen from FIG. 3, the second sleeve 21 has an outwardly open end 23 through which cold air may flow out.

The second sleeve 21 may be manufactured in one single piece. As may be seen from FIG. 4 a-4 c and FIGS. 6 to 7, the second sleeve 21 may, however, comprise an outer sleeve part 21 a and an inner sleeve part 21 b, wherein the inner sleeve part 21 b may possibly be fixed to the outer sleeve part 21 a through gluing. Instead of gluing the outer sleeve part 21 a to the inner sleeve part 21 b, these parts can be connected by means of a snap-on connection. The snap-on connection can be achieved by means of a recess or groove 45 formed on the inside of outer sleeve part 21 a and a corresponding protrusion 46 that can snap into the groove 45. In FIG. 4 b, the outer sleeve part 21 a is separated from the inner sleeve part 21 b. In FIG. 4 c, these parts have been connected to each other to form the second sleeve 21 which is showed connected to the tube body 2. In FIG. 6 and FIG. 7 it is further shown how the outer sleeve part 21 a has a wedge or rail 33 which may engage a groove 32 of the inner sleeve part 21 b, such that the inner sleeve part 21 b is locked against rotation in relation to the outer sleeve part 21 a. If the second sleeve 21 is to be made in one piece, this implies that it will be more difficult to manufacture. By manufacturing the second sleeve 21 in two parts 21 a, 21 b (or more than two parts), that are subsequently assembled, the production is simplified.

As may be seen from e.g. FIGS. 6 to 7, there may be (optionally) an additional component 50, which is placed inside the second sleeve 21. This component is best shown in FIG. 21. As is shown in FIG. 21, the component 50 supports a plurality of vanes 24. Embodiments with only one vane are conceivable, but preferably there is more than one vane. For example, two vanes, three vanes, five or six vanes are conceivable. The vane or vanes 24 is/are arranged between the valve 20 and the outwardly open second end 23 of the second sleeve 21. The vane 24 or vanes 24 serves/serve at least partly to convert a rotating air flow into a straight air flow. The additional component 50 with its vanes 24 therefore constitutes an air flow straightening device. By this straightening of the flow one may reduce the turbulence. This results in a lower noise level at the outlet for cold air. In order to reduce the noise level further, one might add a sound-absorbing filter, which removes the higher frequencies. Embodiments without flow straightening vanes 24 or sound-absorbing filters are, however, also conceivable.

As an alternative to the embodiment shown in FIG. 21, the component 50 in FIG. 4 a may as a whole be designed as a filter of a sound-absorbing material, which completely or partly (preferably completely) fills the outlet for the cold air. In order for the filter to function well as a sound-absorber, it may be suitable to choose a porous material that allows the cold air to pass but absorbs the sound. The material of such a filter may e.g. be plastic foam. It has proved that a filter of plastic foam not only reduces the noise level but also may contribute to reduce the risk for clogging because of ice formation. The axial length of such a filter may in realistic embodiments be 15 to 30 mm, for instance. In a possible embodiment the axial length of the filter (e.g. a filter of plastic foam) may be for example, 25 mm. A possible outer diameter of such a filter may be (for instance) in the range of 10 to 22 mm. Such a sound-absorbing filter may have a round cross section but also other cross sections are conceivable, for instance rectangular, oval or hexagonal.

As may be seen from for example FIGS. 22 and FIG. 23, the outwardly open second end 23 of the second sleeve 21 may be toothed along its circumference, such that it has radially outwardly directed openings 25. If the second open end 23 of the second sleeve 21 would be pressed against a hindrance during the use of the vortex tube 1, air may then flow out through the opening 25, i.e. the air flow from the vortex tube 1 is not blocked. In this way, injury to persons may be avoided if the vortex tube 1 would unintentionally be pressed against the skin of a person.

As may be best seen from FIG. 5, a sound-absorbing filter 27 may be arranged on the tube body 2 in the region for the outlet or outlets 12 for hot air. The sound-absorbing filter 27 is suitably designed as a sleeve. The noise level of the vortex tube may be reduced by the sound-absorbing filter 27. However, embodiments without such a sound-absorbing filter 27 are conceivable.

As may be seen from FIG. 11, for instance, the conduits 14 in the tube body are rearwardly open. The tube body 2 is arranged to be connected, direct or indirectly, to a source of compressed air. One way to achieve this may be that the tube body 2 is designed to be fixed directly to a connection to compressed air. In another embodiment which is shown in FIG. 6, the connection may instead be achieved by a nipple 31 which is screwed on the tube body 2. In the embodiment showed in FIG. 6, the rear end 3 of the tube body 2 has an outer thread 42 that may cooperate with a first inner thread 43 of the nipple 31. In this embodiment, the nipple 31 may have a second inner thread 44 through which the nipple 31 may be mounted on a connection to a source of compressed air. It is realized that the connection of the tube body 2 backwards to a source of compressed air may be designed in many other ways.

FIG. 25 shows how the vortex tube 1 has been fastened with screws (or fastened in another way) on an air blow gun 70 which in its turn may be connected to a container containing compressed air. The air blow gun can then serve as a source of pressurized air.

Another way to utilize the vortex tube 1 of the invention is shown in FIG. 24. In FIG. 24 a plurality of vortex tubes I has been placed together and in parallel in a bunch on a manifold 60.

The vortex tube 1 of the invention functions in the following way. Compressed air is admitted from the rear, possibly through activation of an air blow gun, such as the blow gun shown in FIG. 25. The compressed air enters into the conduits 14 in the rear end 3 of the tube body 2. The compressed air passes through the conduits 14 up to the vortex generator 8 where the compressed air passes the passages 19 (see for instance FIG. 18). From the vortex generator 8 the air enters into the inner channel 7 of the tube body 2 and moves in a vortex backwards in the tube body 2 towards the flow limiting body 10. When the air flow reaches the flow limiting body 10, the air flow will be divided into a hot air flow exiting through the outlet 12 or outlets 12 and a cold air flow moving back in a direction towards the vortex generator 8. The cold air flow passes through the central opening 13 of the vortex generator 8 and out of the vortex tube. If the vortex tube has a valve 20, the cold air that exits the vortex tube will first pass through the opening 13 of the vortex generator and then through the opening 35 of the valve 20. If flow-straightening vanes 24 have been provided in the vortex tube 1, the air flow will pass also these ones.

If a user of the vortex tube 1 wants to reduce the total amount of air, this may be done through screwing/turning the second sleeve 21, such that, thereby, the valve 20 will move axially in the vortex tube 1 and enter farther into the inlet of the vortex generator 8 so that the air flow is throttled. If one instead wants to increase the total air flow, the second sleeve 21 is screwed in the other direction so that the valve 20 moves out of the vortex generator 8.

For adjustment of the ratio between the amount of cold air leaving the vortex tube 1 and the amount of hot air leaving the vortex tube 1, the outer control sleeve 28 (see FIG. 5) is turned such that the first sleeve 17 is axially displaced forwards or backwards in the direction of arrow C. Through displacement of the first sleeve 17 the outlet or outlets 12 will be more or less open so that a larger or smaller share of hot air may leave the vortex tube. In principle, it is conceivable that the outlets 12 are entirely blocked so that no air exits through the outlets 12 for hot air. In such a case, however, no division of the air flow will take place and in such a case the air leaving the vortex tube 1 at the second end will not be cooled. However, if one lets out a certain amount of hot air, the air flow will be divided and cold air will flow out through the opening 13 in the vortex generator 8 and out of the vortex tube 1.

Experiments performed with compressed air which has been added at an overpressure of 4 to 6 bars, have showed that a good cooling effect is obtained when the share of cold air is 30 to 35% and the share of hot air is 65 to 70%. For example, the share of cold air may be 33% and the share of hot air 67%. However, it shall be realized that the share of cold air may be higher than 35% and lower than 30%. However, when the share of cold air increases, the cold air will become gradually warmer; the cooling effect decreases.

Both the tube body 2 and the other components in the vortex tube 1 may be manufactured of basically any material, for instance stainless steel or any other metallic material. However, it has proved that, from a manufacturing point of view, it may be suitable to choose a plastic material. The axially running conduits 14 in the tube body 2 may be difficult to obtain with machining, as they are relatively narrow in relation to their length. As an example, the tube body 2 may be made of a polyamide material, e.g. a material marketed under the trade name HTN PA, but also other choices of material are conceivable.

During experiments with the vortex tube of the invention, it has been possible to obtain an outgoing temperature of the cold air of −34° C. at an overpressure of 5 bars and a starting temperature of +21° C. The temperature of the hot air was then +52° C. The noise level measured was about 70 dB.

In an embodiment which has been considered by the inventor, the vortex tube 1 may have a total length of about 170 mm and an outer diameter of about 20 to 25 mm but the vortex tube may, of course, have other sizes. For instance, embodiments are conceivable where the total length of the vortex tube 1 is in the range of 150 mm to 250 mm and the outer diameter of the vortex tube is larger than 25 mm or smaller than 20 mm.

A second embodiment will now be described with reference to FIG. 26. In the embodiment of FIG. 26 the conduit/conduits 14 for the supply of compressed air does/do not run through the material in the very tube body 2. Instead, there is an outer tube or casing 80 surrounding the tube body 2. The tube body 2 and the outer casing 80 will then form between them a conduit 14 for the supply of compressed air. FIG. 26 shows how the compressed air may run from a rear inlet 90 in the rear end 103 of the vortex tube 1 and up to an inlet 15 to the vortex generator 8. Inside the channel 7 the function is the same as according to the first embodiment and will therefore not be explained further. Cold air leaves the vortex tube 1 through a conduit 300 that ends in an outlet 100 in a front end of the vortex tube 1. The rear end 103 of the vortex tube 1 may be connected to a source of compressed air.

Through the axial design of the conduits 14 for the supply of compressed air (the conduits 14 run in parallel with the inner channel of the tube body 2) a more compact design of the vortex tube is obtained, and the vortex tube 1 thereby becomes easier to handle. The diameter will be smaller as a connection from the side is not needed. In addition, one may easily place several vortex tubes in parallel with each other on a common manifold 60 in the way shown in FIG. 24. This is difficult to achieve if each vortex tube has to have a connection for compressed air which is directed transversely to the longitudinal direction of the vortex tube (see FIG. 1). By means of the vortex tube of the invention it is thus possible to group several vortex tubes together and connect them, via a manifold 60, to a common source of compressed air.

In the embodiment shown in FIG. 26, the vortex tube is, however, not as compact as in the first embodiment where the conduit/conduits for compressed air runs/run through the very wall of the tube body 2 but still the advantage is achieved that several vortex tubes may be grouped together and connected to a common source of compressed air via a manifold 60. As compressed air may be supplied in the axial direction of the vortex tube, it will be easier to use the vortex tube when it has been mounted on an air blow gun, for instance. A bulky radial connection is avoided.

If the conduits 14 for the supply of compressed air run axially (from one end of the tube body 2 up to the inlet to the vortex generator 2, in parallel with the inner channel 7 of the tube body 2) also another advantage is achieved. This design makes it possible to adjust the total air flow by means of a valve 20 fitting into the mouths of the conduits 14.

If the size of the outlet 12 (or outlets 12) for hot air can be adjusted, the ratio between hot air and cold air can easily be adjusted.

If the axially displaceable sleeve 17 is present, the size of the outlet/outlets 12 can easily be adjusted.

By means of the turnable second sleeve 21 and the valve 20 one may easily adjust the total amount of air.

If there is an adjustment possibility for the total air flow (the valve 20) and another adjustment possibility (the axially displaceable sleeve 17) for the adjustment of the ratio between hot air and cold air, one may adjust the total flow independently of the ratio between cold air and hot air. In a corresponding manner, the ratio between hot air and cold air may be adjusted independently of the total air flow.

If the rear end 3itself of the tube body 2 is connectable to a source of compressed air, a more compact design is obtained. 

1. A vortex tube for the generation of cold air, which vortex tube comprises a tube body with a wall, the inner wall surface of which forms an inner channel with a circular-cylindrical cross section, and wherein a vortex generator is arranged in a first end of the channel and a flow limiting body is arranged in a second end of the channel, and wherein at least one outlet for hot air is arranged at the second end of the channel and the vortex generator has an opening through which cold air may leave the channel in a first end of the channel, and wherein the vortex tube further has at least one conduit for the supply of compressed air to the vortex generator, and wherein said at least one conduit for the supply of compressed air extends in the same axial direction as the tube body and extends from a rear end of the vortex tube up to an inlet to the vortex generator, and in that the rear end of the vortex tube is adapted to be connected to a source of compressed air.
 2. A vortex tube according to claim 1, wherein said at least one conduit for the supply of compressed air extends through the wall of the tube body in parallel with the inner channel from a rear end of the tube body up to an inlet to the vortex generator, and in that the rear end of the tube body is adapted to be connected to a source of compressed air.
 3. A vortex tube according to claim 2, wherein the vortex tube has a plurality of conduits for compressed air running through the wall of the tube body in parallel with the inner channel, wherein the conduits for compressed air are distributed around the circumference of the tube body.
 4. A vortex tube according to claim 1, wherein said at least one outlet for hot air which is arranged at the second end of the channel is designed to let out hot air radially outwardly from the tube body.
 5. A vortex tube according to claim 2, wherein the vortex tube is designed such the size of said at least one outlet for hot air can be adjusted.
 6. A vortex tube according to claim 5, wherein an axially adjustable first sleeve is arranged on the tube body and associated with said at least one outlet for hot air so that one may adjust the size of the outlet for hot air through axial displacement of the first sleeve.
 7. A vortex tube according to claim 2, wherein the vortex generator comprises passages which first converge and then diverge in a direction from the inlet of the vortex generator and towards the inner channel of the tube body.
 8. A vortex tube according to claim 2, wherein the vortex tube further comprises a valve, which is arranged to be axially displaced into the vortex generator or out of it, so that a flow of air through the vortex generator may be adjusted thereby.
 9. A vortex tube according to claim 8, wherein the valve is arranged inside a second sleeve, which second sleeve has a first end that is threaded onto the tube body such that, by screwing the second sleeve, one can adjust the position of the valve in relation to the vortex generator, and in that the second sleeve has an outwardly open second end through which cold air may flow out.
 10. A vortex tube according to claim 9, wherein the second sleeve comprises at least one vane arranged between the valve and the outwardly open second end of the second sleeve, which vane is arranged to at least partly convert a rotating air flow into a straight air flow.
 11. A vortex tube according to claim 9, wherein the outwardly open second end of the second sleeve is toothed along its circumference so that an air flow from the vortex tube will not be blocked if the outwardly open end of the second sleeve would be pressed against a hindrance.
 12. A vortex tube according to claim 6, wherein a sound-absorbing filter is arranged on the tube body around the region for the outlet or outlets for hot air. 